The Research Of Cache Consistency Of Mobile Client In Embedded Mobile Real-time Database

With the fast development of mobile telecommunication, many computing nodes can move freely keeping connection with the network. So people urgently want to visit any data at any time and any place. With embedded and mobile computing technology develops gradually mature, Embedded Mobile Real-time Database system (EMRTDBS) has been a hot field. Client data caching technology as a key technology of EMRTDBS is to further enhance the mobile database system performance and scalability. Otherwise, Client caching technology can support disconnections of the client, improve the availability of the mobile database. Client consistency research is one of the most important issues of cache technology research.However, for maintaining client cache consistency, the cached data must consistent with those data stored in the server. The main job is to maintain data synchronization between the client and the server when the data in the server is updated. An effective scheme will support the prolonged disconnection operation. The algorithms must achieve great improvements of transaction latency and minimizes the number of aborted transactions.The proposed scheme ASI uses asynchronous invalidation report (call-backs) to maintain cache consistency i.e. report are broadcast by the server only when some data changes, and not periodically. The client uses the invalidation report to maintain data consistency. The home MSS maintains for each MC a data structure which stores the latest timestamp for each data item cached by MC. MC can continue to use its cache even after prolonged periods of disconnection from the network, without the need of discarding the entire cache. The server broadcasts the Control Message (CM) periodically. Guarantees can be given about when this report will be sent and hence guarantees can be given for the waiting time.ASI is an effective cache maintenance scheme. We compare proposed algorithms to the algorithm based on synchronous cache invalidation scheme called API. Experimental results show the superiority of ASI.